Detonator.



D. CORRIE L G. A. ASHCROFT.

DETONATOR.

APPLICATION FILED 0m10.191s.

l, 167,981 Patented Jan. 11, 1916.

DAVID CUBRIR AND GEORGE ALFRED ASHCROFT, 0F COUNTY 0F STIRLING, SCOTLAND,

ASSL'GNORS TO NOBELS EXPLOSIVES CMPANY, LIMITED, 0F GLASGOW, SCOTLAND.

DETONATOR.

Specication of Letters Patent.

Patented Jan. 11, 1916.

Application {ile/d December 10, 1913. Serial No. 805,695.

To all whom it may concern Be it known that We, DAVID Coram and GEQBGE ALFRED Asr-rcnor'r, subjects of the King of the United Kingdom of Great Britain and Ireland, and both residing at Westquarter Factory, Stirlingshire, Scotland, have invented a certain new and useful Improvement in Detonators, of which the following is a specification.

This invention has for its object the production of a detonator which will not be liable to miss-lire and the manufacture of which is less dangerous and troublesome than in the case of detonators as made heretofore.

lt has hitherto been the usual practice to press into the detonator tube a charge of detonator composition, such for instance as tetranitromethylanilin, then to insert a charge of priming composition, such as fulminate of mercury, and finally to press into the tube so as partially to inclose the priming composition a thimble-shaped member or cap, said memberor cap having cylindrical walls which it more or less closely the interbr of the tube, the open end of the cap being turned to the inside of the detonator and the outer end of the cap being pierced with a small central aperture exposed to the spit of the fuse. With this constriction of the aperture miss-fire is liable to occur Whether for the reason that the end of the fuse has not been truly in register with the aperture in the cap, or because with the detonation of the charge of priming composition the detonator vtube is disrupted, the wave of detonation or explosion being propagated in all directions and the detonator vtube being incapable of withstanding the circumferential or radial strain for sutilcient time to permit the Wave to reach the inforcement is readily obtained by insertion in the detonator tube of a cylinder or cap 4 unobstructed at its outer end and serving to `\retain the charge of priming composition; or the reinforcement may be obtained by constrictlng the diameter of that part of the tube occupied by the charge of priming composltion so that the ratio of the thickness of the wall of the tube in relation to the diameter of the tube is increased at thatpart containing the priming composition without obstruction of the outer end, While the part containing the detonator composition, and indeed the Whole of the remaining length of the tube, is of normal dimensions and form. Or, the desired result may be obtained by thickening 0r strengthening that part of the detonator tube occupied by the priming composition or by constricting the tube at that part only so that the capacity of theitube to resist strain in circumferential or radial direction having regard to the quantity'4 of Y priming composition inclosed thereby will be increased at that part; the reinforced or constricted part of the tube being completely open at the end exposed to the spit of the fuse.

A convenient form of detonator is produced as follows: A charge of detonator composition is first pressed into the tube, then an open-ended or open-topped cylinder, unobstructed at its outer end, is inserted .so as to rest on the charge of detonator composition, and finally a charge of priming composition is pressed into the tube. This charge fills the cylinder and if desired'part of the tube beyond the cylinder, the area of the free surface of the priming composition being in the latter case equal to the Whole cross-sectional area of the tube.

Alternative forms of detonator produced as above described are illustrated in crosssection in Figs. l and 2 of the accompanying drawings. As shown in Fig. 1, A denotes the charge of detonator composition,

e. g., of tetranitromethylanilin, pressed into composition. D denotes the charge of priming composition which in the illustration shown is more than suiicient to fill the interior of the cylinder, after pressing, part of the charge of priming composition extending above the upper end of the cylinder and filling the entire cross section of the tube. The detonator shown in Fig. 2 differs from that shown in Fig. 1 in that for the open-ended cylinder C there has been substituted a cylindrical member C1 open at its outer end and having a dished lower end pierced by a central aperture, that is similar in form to the cap previously used, but inverted, the said member C1 affording a container for the priming composition and acting, as in the case of the form shown 1n Fig. l, to direct the Wave of propagation of explosion axially.

It will be appreciated that with the ernployment of an open-topped cylinder or inverted cap of the form shown in Fig. 2 the wall of the detonator tube is less liable to be torn should the cap be seated at an angle when pressed into the tube than is the case when the usual cap is employed-the sharp edges of the cap being liable, in the latter case, to bite into the tube and tear the same and in certain eventualities to cause press explosions.

It has been ascertained that factors in determining the extent of reinforcement or constriction necessary or most advantageous are the` extension of the charge of priming composition beyond the extremities of the reinforced or constricted part of the tube, and the state of compression of the charge. Thus, Within limits, the thickness or length of the cylinder may be decreased, if the charge of priming composition be increased and the pressure conditions properly adjusted. Further, it is not essential that there should be a layer of fulminate above the upper extremity of the reinforced or constricted part provided that the charge contained within that part is tightly pressed; again, the charge of priming composition may extend to a short distance below the lower extremity of the reinforced or constricted part, always provided, however, that conditions are such as to insure substantially confinement of the wave of detonation to propagation in axial direction for such a duration that the charge of detonator composition may be detonated before disruption of the tube by strain in circumferential or radial direction.

2. A detonator comprising a tube closed at one end and partially filled with a charge of detonator composition, a reinforcing member in said tube consisting of a short tubular member fitting the bore of said first mentioned tube above the charge of detonator composition, and a charge of priming composition Within said reinforcing member, and presenting an igniting surface equal in area to the cross section of the bore of said first mentioned tube, the strength of the Walls of said reinforcing member being so proportioned relative to the charge of the priming composition as to prevent rupture of the tube until the charge of detonator composition has been detonated.

3. A detonator comprising a tube closed at one end and partially filled with a charge of detonator composition, a reinforcing member in said tube consisting of a short tubular member fitting the bore of said first mentioned tubes above the charge of detonator composition, and a charge of priming composition within said reinforcing member and comprising an-igniting surface as large in area as the cross section of the bore of said reinforcing member, the strength of the walls of said reinforcing member being so proportioned relative to the charge of the priming composition as to prevent rupture of the tube until the charge of detonator composition has been detonated.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

DAVID ooRRIE. GEORGE ALFRED AsHoRoFT.

Witnesses:

HENRY MASON, J AMES VICTOR STEWART. 

